CN106537801B - Communication device, circuit, driving device, power supply device, tuning and discovery method - Google Patents

Communication device, circuit, driving device, power supply device, tuning and discovery method Download PDF

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CN106537801B
CN106537801B CN201580038891.2A CN201580038891A CN106537801B CN 106537801 B CN106537801 B CN 106537801B CN 201580038891 A CN201580038891 A CN 201580038891A CN 106537801 B CN106537801 B CN 106537801B
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unit
antenna
capacitor
value
resonance
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CN106537801A (en
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管野正喜
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Dexerials Corp
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Dexerials Corp
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B5/00—Near-field transmission systems, e.g. inductive or capacitive transmission systems
    • H04B5/70—Near-field transmission systems, e.g. inductive or capacitive transmission systems specially adapted for specific purposes
    • H04B5/72—Near-field transmission systems, e.g. inductive or capacitive transmission systems specially adapted for specific purposes for local intradevice communication
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q5/00—Arrangements for simultaneous operation of antennas on two or more different wavebands, e.g. dual-band or multi-band arrangements
    • H01Q5/30—Arrangements for providing operation on different wavebands
    • H01Q5/307—Individual or coupled radiating elements, each element being fed in an unspecified way
    • H01Q5/314—Individual or coupled radiating elements, each element being fed in an unspecified way using frequency dependent circuits or components, e.g. trap circuits or capacitors
    • H01Q5/335—Individual or coupled radiating elements, each element being fed in an unspecified way using frequency dependent circuits or components, e.g. trap circuits or capacitors at the feed, e.g. for impedance matching
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
    • G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
    • G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
    • G06K7/10009—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q7/00—Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/02—Transmitters
    • H04B1/04—Circuits
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/02—Transmitters
    • H04B1/04—Circuits
    • H04B1/0458—Arrangements for matching and coupling between power amplifier and antenna or between amplifying stages
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B5/00—Near-field transmission systems, e.g. inductive or capacitive transmission systems
    • H04B5/20—Near-field transmission systems, e.g. inductive or capacitive transmission systems characterised by the transmission technique; characterised by the transmission medium
    • H04B5/22—Capacitive coupling
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B5/00—Near-field transmission systems, e.g. inductive or capacitive transmission systems
    • H04B5/20—Near-field transmission systems, e.g. inductive or capacitive transmission systems characterised by the transmission technique; characterised by the transmission medium
    • H04B5/24—Inductive coupling
    • H04B5/26—Inductive coupling using coils
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B5/00—Near-field transmission systems, e.g. inductive or capacitive transmission systems
    • H04B5/40—Near-field transmission systems, e.g. inductive or capacitive transmission systems characterised by components specially adapted for near-field transmission
    • H04B5/48—Transceivers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q7/00—Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop
    • H01Q7/005—Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop with variable reactance for tuning the antenna
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B5/00—Near-field transmission systems, e.g. inductive or capacitive transmission systems
    • H04B5/20—Near-field transmission systems, e.g. inductive or capacitive transmission systems characterised by the transmission technique; characterised by the transmission medium
    • H04B5/24—Inductive coupling
    • H04B5/26—Inductive coupling using coils
    • H04B5/263—Multiple coils at either side

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • General Health & Medical Sciences (AREA)
  • Electromagnetism (AREA)
  • Artificial Intelligence (AREA)
  • Computer Vision & Pattern Recognition (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Near-Field Transmission Systems (AREA)

Abstract

Provided is a technique such as a non-contact communication device capable of obtaining good communication characteristics in response to fluctuations in resonance frequency caused by various factors. A non-contact communication device (100) is provided with an antenna resonance unit (110) and an antenna drive unit (130). In the antenna drive unit (130), a measurement unit composed of, for example, a differential amplifier (A3) measures the output current from the oscillation unit (131), and a control unit (140) detects the minimum value or the maximum value of the output current and controls the resonance frequency using the optimum control value corresponding to the minimum value or the maximum value. Therefore, even when the resonance frequency fluctuates due to variations in manufacturing of the antenna characteristics, or due to a use environment or a time change, good communication characteristics based on the set resonance frequency can be obtained.

Description

Communication device, circuit, driving device, power supply device, tuning and discovery method
Technical Field
The present invention relates to a technique of a contactless communication device that performs contactless communication by electromagnetic coupling, a contactless power supply device that performs contactless power supply, and the like.
Background
In recent years, a contactless communication system using nfc (near Field communication), which is a short-range contactless communication technology, has spread remarkably. In such a contactless communication system, a receiving antenna provided in a contactless ic (integrated circuit) card receives a transmission signal output from a transmission antenna (resonance circuit) of a system-dedicated read/write (hereinafter, referred to as R/W) device by an electromagnetic induction action.
In such a contactless communication system, in order to obtain good communication characteristics, it is important to make the frequency of a signal source in the R/W device, the resonant frequency of a transmission antenna of the R/W device, and the resonant frequency of a reception antenna (resonant circuit) in the contactless IC card coincide with each other. However, the resonant frequency of the receiving antenna of the contactless IC card or the transmitting antenna of the R/W device varies depending on various factors. In this case, it is difficult to stably transmit and receive information between the non-contact IC card and the R/W device.
Therefore, in the technical field of the contactless communication system, various techniques for maintaining a good communication state under all conditions have been proposed. Patent document 1 discloses the following technique: a transmitter for performing non-contact communication with the outside by electromagnetic induction is configured to include a transmission antenna, a signal output unit, a monitoring circuit unit, and a correction circuit unit, and to optimize communication characteristics while monitoring a communication state. In this transmission device, a monitoring circuit unit monitors information on a current flowing through an antenna coil, determines a communication state based on the monitored information, and a correction circuit unit corrects a communication characteristic based on a determination result of the monitoring circuit unit (see, for example, paragraph [0137] of patent document 1).
Documents of the prior art
Patent document
Patent document 1 Japanese patent laid-open publication No. 2013-58170
Disclosure of Invention
Problems to be solved by the invention
As described above, the resonant frequency of the antenna varies due to various factors. For example, it varies due to variations in antenna characteristics in manufacturing, usage environment, time variation, and the like. New measures against the resonance frequency variation based on these factors are expected.
The present invention aims to provide a technique of a non-contact communication device or the like capable of coping with a variation in resonance frequency due to the above-mentioned factors and obtaining a good communication characteristic.
Means for solving the problems
In order to achieve the above object, a contactless communication device according to one aspect of the present invention includes an antenna resonance unit, an oscillation unit, a measurement unit, and a control unit.
The antenna resonance section includes an antenna coil and a capacitor section having a variable-capacity capacitor.
The oscillation unit can output a signal having a predetermined oscillation frequency to the antenna resonance unit.
The measurement unit is configured to measure an output current from the oscillation unit to the antenna resonance unit.
The control unit is configured to detect a minimum value or a maximum value of the measured output current, and control the resonance frequency of the antenna resonance unit using a control value in an arbitrary range including an optimum control value at which the output current is at a minimum or a maximum, among control signals for controlling the capacitance of the variable capacitor of the capacitor unit.
In the contactless communication device, the measurement unit measures an output current from the oscillation unit, the control unit detects a minimum value or a maximum value of the output current, and the resonance frequency is controlled using a control value including an optimum control value corresponding to the minimum value or the maximum value. Therefore, even when the resonance frequency varies due to various factors, good communication characteristics based on the set resonance frequency can be obtained.
The oscillation frequency may be an oscillation frequency offset from a prescribed frequency. The "predetermined frequency" is the frequency of the signal at which the antenna current becomes the minimum value or the maximum value. The "shifted oscillation frequency" is an oscillation frequency at which the output current (for example, LSI current) becomes a minimum value or a maximum value.
The control unit may perform control using a value that is offset from a control value at which the output current is minimum or maximum, among the control values in the arbitrary range.
The oscillation unit and the measurement unit may be provided in an antenna driving unit connected to the antenna resonance unit.
This eliminates the need to provide a resistor and wiring for monitoring the antenna current in the antenna resonance section between the antenna resonance section and the antenna driving section as in patent document 1, and thus enables a simple circuit configuration to be formed. In addition, noise is less likely to be generated, and favorable communication characteristics can be obtained.
The contactless communication device may further include a storage unit that stores the optimal control value.
For example, even when the resonance frequency changes due to the use environment of the device or a change over time after the manufacture of the contactless communication device (after factory shipment), the control unit obtains the communication characteristics at the optimum resonance frequency by using the stored optimum control value.
The contactless communication device may further include a gain controller that adjusts a gain of a signal output from the oscillation unit. Further, the control unit may be configured to set the gain, which is one of the antenna parameters, to a first value during a communication period, and to set the gain to a second value different from the first value during a detection period of a minimum value or a maximum value of the output current.
In this case, the second value may be greater than the first value. Thus, the SN ratio of the signal can be increased during the detection period, and the control unit can obtain an accurate optimum control value.
The capacitor part may include at least 1 of the series resonance capacitor part and the parallel resonance capacitor part, or both of them.
The parallel resonant capacitor section may have the variable capacitance capacitor, and the series resonant capacitor section may have a fixed capacitance capacitor. Alternatively, the parallel resonant capacitor section may have a fixed-capacity capacitor, and the series resonant capacitor section may have the variable-capacity capacitor. Alternatively, the parallel resonant capacitor section and the series resonant capacitor section may have the variable capacitance capacitor, respectively.
An antenna circuit according to an aspect of the present invention is an antenna circuit of a contactless communication device including the oscillation unit, the measurement unit, and the control unit, and includes the antenna resonance unit, an input line, and a control signal line.
The input line is configured to input a signal having a predetermined oscillation frequency set by the oscillation unit.
The control signal line is configured to be connected to the variable capacitance capacitor. A control signal line is supplied with a control value in an arbitrary range including an optimum control value. The optimum control value is an optimum control value among control signals for controlling the capacitance of the variable capacitance capacitor, which are output from the control unit, and corresponds to a minimum value or a maximum value of the output current from the oscillation unit to the antenna circuit, which is measured by the measurement unit.
An antenna driving device according to an aspect of the present invention is configured to drive the antenna resonating section, and includes the oscillating section, the measuring section, and a control value input section that inputs a control value including the optimal control value.
The above-described contactless communication device can also be applied to a contactless power supply device.
A tuning method according to an aspect of the present invention is a tuning method for a resonance frequency of the antenna resonance unit, including the following operations: the oscillation unit sets a predetermined oscillation frequency of a signal output to the antenna resonance unit.
An output current from the oscillator to the antenna resonator is measured.
Detecting a minimum value or a maximum value of the measured output current.
A control value is stored in a storage unit, the control value being a control value in an arbitrary range including an optimum control value at which the output current becomes minimum or maximum, among control signals for controlling the capacitance of the variable capacitance capacitor of the capacitor unit.
A discovery (discovery) method according to an aspect of the present invention is a discovery method performed by a contactless communication device having the antenna resonance unit, and includes the following operations: the presence of the partner side device is detected in an R/W (read/write) mode.
In a case where the presence of the partner side device is not detected, the presence of the partner side device is detected in the card mode.
When the presence of the counterpart device is not detected in the card mode, an optimum control value in a control signal for controlling the capacitance of the variable capacitance capacitor is detected, and the tuning process of the resonance frequency of the antenna resonance section is executed.
The execution of the tuning process may comprise the actions of: and storing the control value in an arbitrary range including the optimum control value in a storage unit. The optimum control value may be a control value at which the phase of an antenna current, which is a current flowing through the antenna coil, becomes 0, a control value at which the phase of the antenna current becomes minimum or maximum, a control value at which the phase of an impedance becomes 0, a control value at which the phase of an output current from the oscillation unit to the antenna resonance unit becomes 0, or a control value at which the output current becomes minimum or maximum.
The execution of the tuning process may comprise the actions of: the oscillation unit sets a predetermined oscillation frequency of a signal output to the antenna resonance unit. Further, the performing of the tuning process may comprise the acts of: the control device measures an output current from the oscillation unit to the antenna resonance unit, detects a minimum value or a maximum value of the measured output current, and stores a control value in the control signal in an arbitrary range including the optimum control value at which the output current is minimum or maximum in the storage unit.
In a case where the presence of the partner-side device is not detected in the card mode, the following processing may be performed. That is, the detection in the R/W (read/write) mode and the detection in the card mode are sequentially repeated, and the tuning may be performed when a time out elapses between the repeated processing of the detection in the R/W mode and the detection in the card mode.
A program according to an aspect of the present invention is a program for causing the contactless communication device or the contactless power supply device to execute the tuning method. Alternatively, a program according to an embodiment of the present invention is a program for causing a non-contact communication apparatus to execute the discovery method.
Effects of the invention
As described above, according to the present invention, it is possible to cope with a variation in resonance frequency due to various factors, and it is possible to obtain a good communication characteristic.
Drawings
Fig. 1 is a block diagram showing a configuration of a contactless communication system according to an embodiment of the present invention.
Fig. 2 shows a circuit configuration of a contactless communication device according to a first embodiment of the present invention.
Fig. 3(a) shows a single-drive type impedance matching circuit, and fig. 3(B) shows a differential-drive type impedance matching circuit. Fig. 3C shows a modification of fig. 3(B), and fig. 3(D) shows a modification of fig. 3 (a).
The upper part of fig. 4 is a graph showing characteristics of the LSI current and its phase, and the antenna current flowing through the antenna and its phase. The lower part of fig. 4 is a graph showing characteristics of impedance and its phase when the antenna is viewed from the antenna driving part.
Fig. 5 is a graph showing a deviation between the resonance point (frequency of phase 0) and the frequency at which the impedance is minimum in an enlarged manner.
Fig. 6 is a graph showing a general relationship between the capacity and the impedance of the parallel resonance capacitor at the resonance frequency.
Fig. 7 is a graph showing the relationship between the resonance frequency and the LSI current at different inductances of the antenna coil.
Fig. 8 is a flowchart showing a process in which the contactless communication apparatus automatically tunes the resonant frequency when the contactless communication apparatus is shipped from the factory.
Fig. 9 is a timing chart illustrating the process illustrated in fig. 8.
Fig. 10 is a flowchart showing a process in which the contactless communication apparatus automatically tunes the resonant frequency after factory shipment of the contactless communication apparatus.
Fig. 11 is a timing chart showing the process shown in fig. 10.
Fig. 12 shows a circuit configuration of a contactless communication device according to a second embodiment of the present invention.
Fig. 13 shows a circuit configuration of a contactless communication device according to a third embodiment of the present invention.
Fig. 14 is a block diagram showing a configuration of a contactless power supply system in a mode in which the technique of the contactless communication system shown in fig. 1 is applied to the contactless power supply system 2.
Fig. 15 shows a sequence from detection of a power receiving device in a power supply device (equipment detection) to charging (power transmission).
Detailed Description
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[ first embodiment ]
(non-contact communication System)
Fig. 1 is a block diagram showing a configuration of a contactless communication system according to an embodiment of the present invention. In fig. 1, between the circuit blocks, lines related to input and output of information are indicated by solid arrows, and lines related to supply of electric power are indicated by broken arrows.
The contactless communication system 1 according to one embodiment of the present invention is applied to NFC (near Field communication) as a short-range wireless communication technology including NFC-A, NFC-B, NFC-F based on international standard specification ISO/IEC18092, and wpc (wireless Power consortium) as a contactless Power supply technology. That is, the present invention is applied to a communication/power supply system that performs communication and power supply in a non-contact manner by electromagnetic induction between coils of a 2-time antenna unit of a 1-time antenna unit.
The contactless communication system 1 includes a transmitting device 100 and a receiving device 200. The transmission device 100 functions as a contactless communication device. The contactless communication system 1 performs information transmission and reception between the transmission device 100 and the reception device 200 by contactless communication. Further, as an example of the contactless communication system 1, for example, a communication system in which Felica (registered trademark) is a representative and a contactless IC card specification and an NFC specification are combined is given.
(transmitting device (non-contact communication device))
The transmission apparatus 100 will be explained. The transmission device 100 has a read/write (R/W) function capable of reading and writing data from and to the reception device 200 in a contactless manner. As shown in fig. 1, the transmission device 100 includes an antenna resonance unit (antenna circuit) 110, a system control unit 118, a modulation circuit 116, and a demodulation circuit 117.
The antenna resonance section 110 includes a1 st-order side antenna section 111 and an impedance matching section 112, and forms a resonance circuit including an antenna coil and a resonance capacitor (capacitor section having a variable capacitance capacitor) as described later. The signal is transmitted and received between the antenna resonance unit 110 and the 2 nd-side antenna unit 201 of the receiving apparatus 200 by electromagnetic coupling.
The transmission/reception control unit 113 includes a voltage generation circuit (mainly, DAC133 described later) for adjusting the capacitance of the resonant capacitor, and a measuring device (mainly, differential amplifier a3 and ADC134 described later) for measuring the output current of the antenna driving unit (antenna driving device) 130. The 1 st-order antenna unit 111 has a function of transmitting a transmission signal of a desired frequency through a resonant circuit and receiving a response signal from the receiving device 200 described later.
The impedance matching section 112 has a function as a matching circuit that matches the impedance between the transmission signal generating section 114 and the 1 st-order side antenna section 111. Although not shown in fig. 1, the impedance matching section 112 has a variable capacitance capacitor (hereinafter, referred to as a variable capacitor). In the present embodiment, the capacitance of the variable capacitor is adjusted by the voltage generation circuit as described later, thereby achieving the optimization of the impedance matching and the resonant frequency between the transmission signal generation unit 114 and the 1 st-order side antenna unit 111.
As the variable capacitor, typically, a small ceramic type variable capacitor is used. BaSrTiO3 or the like is used as a ferroelectric material, and the relative permittivity of the material is changed to change the capacitance. As the variable capacitor, a type using an RF switch or a mems (micro Electro Mechanical systems) type may be used.
The transmission signal generation unit 114 has the following functions: a carrier signal of a desired frequency (for example, 13.56MHz) is modulated by transmission data input from the modulation circuit 116, and the modulated carrier signal is output to the 1 st-order side antenna unit 111 via the impedance matching unit 112.
The modulation circuit 116 has the following functions: the transmission data input from the system control unit 118 is encoded, and the encoded transmission data is output to the transmission signal generation unit 114.
The demodulation circuit 117 has the following functions: the response signal received by the 1 st-order-side antenna unit 111 is acquired via the impedance matching unit 112, and is demodulated. Further, the demodulation circuit 117 has a function of outputting the demodulated response data to the system control unit 118.
The system control unit 118 has the following functions: various control signals for control are generated in accordance with an external command or a built-in program, and the control signals are output to the modulation circuit 116 and the transmission/reception control unit 113 to control the operations of the two circuit units. The system control unit 118 also has the following functions: transmission data corresponding to the control signal (command signal) is generated and supplied to the modulation circuit 116. The system control unit 118 also has a function of performing predetermined processing based on the response data demodulated by the demodulation circuit 117.
In the example shown in fig. 1, the transmission/reception control unit 113 and the system control unit 118 are provided independently in the transmission device 100, but the contactless communication system 1 according to the embodiment of the present invention is not limited to this example. For example, as the transmission/reception control unit 113 is included in the system control unit 118, another circuit configuration may be adopted.
(receiving apparatus)
Next, the receiving apparatus 200 will be explained. In addition, in the example shown in fig. 1, an example is shown in which the reception apparatus 200 is constituted by a non-contact IC card (data carrier). In this example, an example in which the receiving apparatus 200 has a function of adjusting its own resonance frequency will be described.
As shown in fig. 1, the receiving apparatus 200 includes a 2-time side antenna unit 201 having a function as a receiving antenna, a rectifying unit 204, a reception control unit 202, a demodulation circuit 205, a system control unit 203, a modulation circuit 206, a constant voltage unit 207, and a battery 208.
The 2 nd-side antenna unit 201 has a resonant circuit including a resonant coil and a plurality of resonant capacitors, for example, which are not shown. The resonance capacitor is a structure including a variable capacitor that changes capacitance by applying a control voltage. The 2 nd-side antenna section 201 has the following functions: the 1 st-order antenna unit 111 of the transmission device 100 communicates by electromagnetic coupling, receives a magnetic field generated by the 1 st-order antenna unit 111, and receives a transmission signal from the transmission device 100. At this time, the capacitance of the variable capacitor is adjusted so that the resonance frequency of the 2 nd-side antenna unit 201 becomes a desired frequency.
The rectifier 204 is, for example, a half-wave rectifier circuit including a rectifying diode and a rectifying capacitor, and the rectifier 204 has the following functions: the ac power received by the 2 nd-side antenna unit 201 is rectified into dc power, and the rectified dc power is output to the constant voltage unit 207.
The constant voltage part 207 has the following functions: the electric signal (dc power) input from the rectifier 204 is subjected to voltage fluctuation (data component) suppression processing and stabilization processing, and the dc power after the processing is supplied to the reception controller 202. The dc power output via the rectifier 204 and the constant voltage unit 207 is used as a power supply for operating the IC in the receiver 200.
The reception control unit 202 has the following functions: the resonance characteristics of the 2 nd-side antenna unit 201 are controlled to optimize the resonance frequency at the time of reception. Specifically, the control voltage is applied to the variable capacitor included in the 2 nd-side antenna unit 201 to adjust the capacitance thereof, thereby adjusting the resonance frequency of the 2 nd-side antenna unit 201.
The demodulation circuit 205 has the following functions: the received signal received by the 2-time side antenna unit 201 is demodulated, and the demodulated signal is output to the system control unit 203.
The system control unit 203 has the following functions: the content of the signal demodulated by the demodulation circuit 205 is determined, necessary processing is performed, and the modulation circuit 206 and the reception control unit 202 are controlled.
The modulation circuit 206 has the following functions: the received carrier is modulated in accordance with the result (contents of the demodulated signal) determined by the system control unit 203, and a response signal is generated. The modulation circuit 206 has a function of outputting the generated response signal to the 2 nd-side antenna unit 201. The response signal output from the modulation circuit 206 is transmitted from the secondary-side antenna section 201 to the primary-side antenna section 111 by non-contact communication.
The battery 208 has a function of supplying electric power to the system control unit 203. The battery 208 is charged by connecting its charging terminal to the external power supply 50. As in the example shown in fig. 1, when the receiving device 200 has a structure in which the battery 208 is incorporated, more stable power can be supplied to the system control unit 203, and stable operation can be performed.
The receiving apparatus 200 may be configured to drive the system control unit 203 using dc power generated via the rectifier 204 and the constant voltage unit 207 without using the battery 208.
In the contactless communication system 1 of the present embodiment, data communication is performed in a contactless manner by electromagnetic coupling between the 1 st-order antenna unit 111 of the transmission device 100 and the 2 nd-order antenna unit 201 of the reception device 200. Therefore, in the transmission device 100 and the reception device 200, in order to perform communication efficiently, the respective resonance circuits of the 1 st-order antenna unit 111 and the 2 nd-order antenna unit 201 are configured to resonate at the same carrier frequency (for example, 13.56 MHz).
(Circuit configuration of non-contact communication device)
Fig. 2 shows a circuit configuration of the transmitting apparatus 100, i.e., the contactless communication apparatus. The contactless communication device includes an antenna resonance unit 110, a filter unit 120, an antenna drive unit 130, a control unit 140, and a storage unit 141.
The antenna resonance section 110 has an antenna coil L3 and an impedance matching section 112. The antenna resonance section 110 is configured such that the impedance matching section 112 is connected to the antenna coil L3. The impedance matching unit 112 prevents impedance mismatch between the antenna driver 130 and the antenna coil L3, and makes the load of the antenna driver 130 constant and pure resistance regardless of the antenna coil L3.
Specifically, the antenna resonance section 110 is configured as a series-parallel resonance circuit in which variable capacitors (parallel resonance capacitor sections) VC1 are connected in parallel and capacitors C2 and C5 (series resonance capacitor sections) having fixed capacities are connected in series, for example. In the variable capacitor VC1, the capacitance changes due to a change in the control voltage (control signal) input thereto, and the resonance frequency of the antenna resonance section 110 changes accordingly. Further, a plurality of variable capacitors may be provided, and the capacities of the plurality of variable capacitors may be changed by the same control voltage value.
The capacitors C7 and C8 have a function of DC cut (DC cut) for preventing the control voltage (DC voltage) applied to the variable capacitor VC1 from leaking to the antenna coil L3. The capacitors C9 and C10 are additional capacitors for absorbing the antenna characteristic difference caused by the antenna size difference or the like.
The impedance matching unit 112 has damping resistors R1 and R2 that determine the Q value (sharpness) of the antenna resonance unit 110.
The filter unit 120 has coils L1, L2, capacitors C1, and C4, and has an emc (electro Magnetic compatibility) function. The high-frequency oscillation signal (the transmission signal) output from the antenna driving unit 130 is a rectangular wave. The filter unit 120 has a function of removing high-frequency noise caused by the oscillation signal. Coils L1 and L2 are connected to one terminals of capacitors C2 and C5, respectively. Capacitors C1, C4 are connected between the coils L1, L2, respectively, and ground.
The antenna driving unit 130 includes an oscillation unit 131 capable of controlling an oscillation frequency, an output unit 135 for supplying an oscillation signal obtained by the oscillation unit 131 to the antenna resonance unit 110, and a gain controller 132 for controlling an output gain of the oscillation unit 131. Further, the antenna driving unit 130 includes: a DAC (digital/analog converter) 133 that converts a digital control voltage value from the control unit 140 described later into an analog signal; a measurement unit including a differential amplifier a3, which measures an output current from the output unit 135; and an ADC (analog/digital converter) 134 which inputs the output signal of the differential amplifier and converts it into a digital signal. The antenna driving unit 130 is formed of, for example, lsi (large Scale integration).
Further, the contactless communication device includes: a control unit 140 that controls the oscillation frequency of the oscillation unit 131 and the antenna resonance frequency of the antenna resonance unit 110; and a storage unit 141 that stores setting values such as antenna parameters and oscillation frequency of the oscillation unit 131. The control unit 140 corresponds to the transmission/reception control unit 113, the system control unit 118, or an element that functions as a single unit in fig. 1.
The oscillator 131 is composed of a variable frequency oscillator that can be controlled in a wide range of oscillation frequencies, for example, 12 to 17MHz, by a frequency control signal supplied from the controller 140. In particular, the oscillator 131 is configured to be able to output a signal having an oscillation frequency set to be shifted from a predetermined frequency to the antenna resonance unit 110 as described below.
In the present embodiment, the "predetermined frequency" is a design value determined by designing inductance, Q value, impedance, and the like of the antenna resonance unit 110 as described later, and is a frequency at which the impedance phase becomes 0. These are design values that determine the antenna characteristics. The frequency at which the impedance phase becomes 0 may be matched with 13.56MHz, which is a standard value, or may be misaligned and shifted.
In the present embodiment, the target frequency of the final oscillation frequency obtained by shifting from the predetermined frequency may be 13.56MHz, which is a standard value, or may be set to a value near the standard value, which is different from the standard value, depending on the manufacturer. As will be described later, the target frequency is a frequency at which the output current (also referred to as an LSI current in the following description) of the antenna driving unit 130 becomes minimum or maximum.
That is, the predetermined frequency and the target frequency are different intrinsic values depending on the manufacturer or the product model.
The output unit 135 includes a pair of differential amplifiers a1 and a2 that output the high-frequency oscillation signal supplied from the oscillation unit 131 as a positive-phase oscillation signal and a negative-phase oscillation signal.
The measurement unit is connected to the input terminal and the output terminal of the differential amplifier a1 of the output unit 135. The measurement unit measures the output current (I _ LSI, hereinafter referred to as LSI current) of the differential amplifier a 1. The LSI current is measured by converting the voltage difference between the voltage V1 of the oscillation signal input to the differential amplifier a1 and the voltage V2 of the positive-phase oscillation signal output from the differential amplifier a1 by means of an output resistor. The measurement unit supplies the measurement result to the control unit 140 via the ADC 134.
The control unit 140 has a function of controlling the R/W function and the card function of the contactless communication device. The R/W function is a function of the contactless communication apparatus as a transmission apparatus shown in fig. 1 to perform communication (reading and writing of data) with a reception apparatus 200 that is a 2-time side device (a partner side device). The card function refers to a function as the 2 nd-side device shown in fig. 1, that is, the receiving apparatus 200, and the contactless communication apparatus has the function.
The control unit 140 controls the control voltage applied to the variable capacitor VC1 so that the resonance frequency of the antenna resonance unit 110 becomes a predetermined frequency. The DAC133 converts the digital control voltage value output from the control section 140 into an analog control voltage signal Vcnt, and applies the analog control voltage signal Vcnt to the variable capacitor VC1 via the control signal line 119 of the antenna resonance section 110. This enables the impedance of the antenna resonance unit 110 to be changed at a high speed of 1ms or less. The control unit 140 is constituted by, for example, a cpu (central Processing unit).
In the antenna driving unit 130, a terminal or a line to which a control voltage value from the slave control unit 140 is input is a control value input unit 139.
As basic matching circuits used for non-contact communication in an NFC system or the like, there are circuit configurations of the type shown in fig. 3(a) to 3(D), respectively. The type shown in fig. 3(a) is a single drive type in which the antenna coil L3 is driven by 1 channel, and the type shown in fig. 3(B) is a differential drive type in which the antenna coil L3 is driven by 2 channels. Both of which act essentially the same. The Tx1 terminal and the Tx2 terminal become driving terminals of the antenna driving section 130. The matching circuit shown in fig. 3(C) is a modification of fig. 3(B), and is used for contactless communication as in fig. 3 (B). The matching circuit shown in fig. 3(D) has a series resonant circuit configuration in the modification of fig. 3A, and is often used for contactless power supply.
The antenna resonance section 110 in the contactless communication device has a differential drive type circuit configuration in which the antenna coil L3 is driven by 2 channels.
In fig. 2, in antenna resonance unit 110, lines connected to Tx1 terminal and Tx2 are input lines 129 to which oscillation signals from oscillation unit 131 are input. In the case of 2 channels, the input lines 129 are 2, and in the case of 1 channel, the input lines 129 are 1.
In the R/W mode, the control unit 140 performs the following control: the oscillator 131 is oscillated at any frequency in the above frequency range, and the positive-phase oscillator signal and the negative-phase oscillator signal having the above frequency are output from the output unit 135 to the Tx1 terminal and the Tx2 terminal.
In the card mode, the control unit 140 performs the following control: the reception signal induced in the antenna coil L3 of the antenna resonance section 110 is detected by a reception circuit not shown, and responded by load modulation.
The upper part of fig. 4 is a graph showing characteristics of the LSI current and its phase, and the antenna current flowing through the antenna coil L3 and its phase. The lower part of fig. 4 is a graph showing characteristics of the impedance (impedance when the antenna is viewed from the antenna driving part 130) and the phase thereof. The solid line indicates the impedance (Ω) and the dotted line indicates the phase (deg). The horizontal axis is frequency. The left vertical axis of the upper part is the current value, the right vertical axis is the phase, the left vertical axis of the lower part is the impedance, and the right vertical axis of the lower part is the phase.
As in the present embodiment, in the series-parallel resonant circuit, as shown in the lower graph, there are 2 resonance points (first phase 0 point, second phase 0 point) where the impedance phase is 0. The resonance point at the lower frequency is a point at which the impedance phase changes from negative to positive, and is mainly a series resonance point between the capacitors C2 and C5 and the antenna coil L3, which are series resonance capacitor units. By the series resonance, there is a frequency at which the impedance becomes minimum. The impedance is minimized at a frequency lower than the frequency of phase 0 due to the influence of a variable capacitor VC1 or the like, which is a parallel resonant capacitor in the series-parallel resonant circuit.
The resonance point at the higher frequency is a point at which the impedance phase changes from positive to negative, and is mainly the parallel resonance point of variable capacitor VC1 and antenna coil L3. By the parallel resonance, there is a frequency at which the impedance becomes maximum. Due to the influence of the capacitors C2 and C5, which are series resonant capacitors in the series-parallel resonant circuit, the impedance becomes maximum at a frequency higher than the frequency of phase 0.
Here, as a general design, there are two methods of making the series resonance point coincide with the system frequency (for example, 13.56MHz) and making the parallel resonance point coincide with the system frequency, and one of them can be selected depending on the LSI used.
The amount of deviation between the resonance point (the frequency of phase 0) and the frequency at which the impedance is minimum or maximum varies depending on the designed values of the inductance, Q value, impedance, and the like of the antenna coil. Fig. 5 is a graph showing the deviation in an enlarged manner. The graph shows the result of calculating the impedance of the antenna and each current of the antenna resonance unit 110 by changing the oscillation frequency of the oscillation unit 131 while fixing the series-parallel resonance capacitors. Here, an antenna having an L of 1.25uH is used, and the antenna is designed so that the series resonance point coincides with, for example, 13.56MHz and the impedance Z is 8 Ω (low impedance type). In contrast, fig. 4 shows an example in which the parallel resonance point is made to coincide with 13.56MHz, and the respective currents are an antenna current, an LSI current, and a filter current (a current flowing through the filter unit 120).
As shown in fig. 5, it can be found that the antenna current has a peak at 13.56MHz as designed, and the frequency at which the impedance becomes minimum and the frequency at which the LSI current becomes maximum deviate from 13.56MHz to 13.46MHz, which is a frequency of 100KHz magnitude.
As described above, since a deviation occurs between the resonance point (the frequency of phase 0) (see fig. 4) and the frequency at which the impedance is minimum or maximum, the target frequency based on the offset value (the deviation amount) is set as described above in order to correct the deviation. For example, the offset value is calculated and actually measured for each product model to determine the offset value.
Here, a low-impedance antenna device of a type in which the series resonance point is made to coincide with 13.56MHz is easily affected by the output resistance of an LSI, and is generally used in combination with an LSI having an output resistance of 1 Ω or less. Since the series resonance point is used, the impedance changes little and stably with respect to the deviation of the resonance frequency in the vicinity of the resonance point.
On the other hand, a high-impedance antenna device of a type (for example, see a graph shown in fig. 4) in which the parallel resonance point is aligned with 13.56MHz is generally used in combination with an LSI having an output resistance of several Ω, because it is less affected by the output resistance of the LSI even if the output resistance of the LSI is large. The impedance is increased by using the parallel resonance point, which has an advantage that the LSI current can be reduced.
In the example shown in fig. 4, the characteristics of the high-impedance type (for example, 80 Ω) antenna device of the type in which the parallel resonance point is made to coincide with 13.56MHz as described above are shown. Here, in the present embodiment, an example of designing a matching constant of a high-impedance antenna device will be mainly described.
Fig. 6 is a graph showing a general relationship between the capacitance and the impedance of the parallel resonant capacitor section at the resonant frequency. (the relationship (characteristic) in the graph is general, and the numerical value itself is not general.) the inductance of the antenna coil is 1.25 μ H. The relationship between the resonance frequency and the capacitance can be approximated by a straight line. The impedance peaks around 13.56 MHz. It can be seen that by changing the capacity of the parallel resonant capacitor, the resonant frequency and impedance can be changed.
Fig. 7 is a graph showing the relationship between the resonance frequency and the LSI current when the antenna coil has different inductances (L ═ 0.75 μ H, 1.0 μ H, 1.25 μ H, and 1.5 μ H). The minimum value of the LSI current is uniform regardless of the inductance of the antenna coil. It is thus seen that, irrespective of the inductance, a frequency at which the resonance frequency ≈ LSI current is minimum holds. That is, the inventors of the present invention have found that when tuning the resonance frequency by using the oscillation frequency shifted from the predetermined frequency as the target frequency and changing the capacitance of the parallel resonant capacitor of the series-parallel resonant circuit and using the parallel resonant point, it is sufficient to measure the LSI current and detect the minimum value while changing the capacitance of the parallel resonant capacitor. In the case of tuning the resonance frequency using the series resonance point, on the contrary, the maximum value of the LSI current may be detected while changing the capacity of the parallel resonance capacitor.
Thus, as shown in fig. 4, the resonance frequency at which the phase is actually 0 is deviated from the frequency at which the impedance becomes maximum (LSI current is minimum). Therefore, as described above, the designer estimates a predetermined frequency and a deviation amount (offset value) from the predetermined frequency in advance based on the design value (inductance, Q value, impedance, etc.) of the antenna resonance unit 110 and the frequency at which the LSI current becomes minimum, and stores these values in the storage unit 141 (see fig. 2), for example. In this case, the target frequency, which is the frequency obtained by the offset, may be stored, or both the predetermined frequency and the offset value may be stored.
In order to obtain the target frequency, the control unit 140 outputs an optimum control value, which is a control voltage signal for the variable capacitor VC1, for obtaining the minimum value of the LSI current. In this case, for example, as shown in fig. 4, when the parallel resonance point deviates to the low side from a predetermined frequency (typically 13.56MHz), the target frequency, which is the frequency for tuning, is set to be lower than the parallel resonance point by an offset value.
The same applies to the case where the resonance frequency is tuned using the series resonance point by changing the parallel resonance capacitor of the series-parallel resonance circuit, i.e., variable capacitor VC 1. In this case, the resonance frequency that actually becomes phase 0 and the frequency at which the impedance becomes minimum are deviated as shown in fig. 4. In order to shift the series resonance point from a predetermined frequency (typically 13.56MHz) to the high side, the target frequency may be set to be higher than the series resonance point by an offset value.
As described above, in order to optimize the communication characteristics depending on manufacturers, a frequency deviated from 13.56MHz, which is empirically obtained, may be set as the target frequency.
The contactless communication device according to the present embodiment can mount a tuning function on an LSI at low cost as will be described later by performing tuning using an LSI current instead of the antenna current shown in patent document 1. However, as shown in fig. 5, the resonance frequency at which the impedance phase (see fig. 4) becomes 0 and the maximum value of the antenna current are well matched, but the minimum value or the maximum value of the LSI current is deviated, which becomes a factor of error. Therefore, by correcting this deviation as an offset, accurate tuning can be performed.
As described above, in addition to storing the offset value as the frequency, the frequency offset may be converted into a capacitance offset according to the characteristic of the capacitance versus the resonance frequency shown in fig. 6, for example, and stored as a voltage value corresponding to the capacitance offset. In this case, in the manufacturing stage, the resonance frequency is tuned by using a predetermined frequency without a shift, and a voltage corresponding to the shift is added to the obtained voltage value, whereby an effect equivalent to the frequency shift can be obtained. In this case, there are the following advantages: since frequency shift is not required, when the predetermined frequency is 13.56MHz, which is the system frequency, the oscillation frequency of the oscillation unit 131 can be set to 13.56MHz, which is the fixed frequency, and the circuit of the LSI is simplified.
(processing of non-contact communication device)
< factory delivery >
Fig. 8 is a flowchart showing a process in which the contactless communication apparatus automatically tunes the resonant frequency when the contactless communication apparatus is shipped from a factory.
As the initialization, the control unit 140 reads the target frequency f0, which is shifted from the predetermined frequency, from the storage unit 141, and sets the target frequency f0 in the oscillation unit 131 (step 101).
As the initialization, the control unit 140 sets the antenna parameters stored in advance in the storage unit 141 in the internal register of the control unit 140, the gain controller 132, and the like (step 102). The antenna parameters include, for example, impedance, Q value, gain of an oscillation signal output from the oscillation unit 131, and a control voltage value (here, 0V as an initial value) of the DAC133 for the variable capacitor VC 1.
The control unit 140 increases the control voltage value for the DAC133 from 0V to a unit voltage one by one, for example, at each step, and measures the LSI current by the measurement unit at each step (step 103). For example, the control unit 140 increases the control voltage value to 3V, which is the maximum value of the system voltage. When the control unit 140 detects the minimum value of the LSI current between 0 and 3V (yes in step 104), the control unit 140 stores the optimum control value, which is the control voltage value for the DAC133 when the LSI current is the minimum, in the storage unit 141 (step 105).
Further, the control unit 140 does not necessarily have to increase the control voltage value to 3V, and if the control unit 140 detects the minimum value in the middle of the increase of the control voltage value from 0V, the process may proceed to step 105 at that point.
When the low-impedance antenna resonance unit 110 of the type that matches the series resonance point with the target frequency is used, the maximum value of the LSI current is detected in step 104.
Then, the control unit 140 sets the oscillation frequency for communication (for example, 13.56MHz) in the oscillation unit 131 (step 106). The control unit 140 sets the antenna parameters for communication (step 107), and ends the tuning process. One of the antenna parameters for communication is an optimum control value stored in the storage unit 141. That is, at the time of communication, the control unit 140 controls the resonance frequency using the optimum control value stored in the storage unit 141.
As will be described below, there are different parameters for the antenna for communication from those for tuning. One example of the parameter is a gain based on an oscillation signal of the oscillation unit 131.
Fig. 9 shows a timing chart of the process shown in fig. 8. The horizontal direction schematically shows the passage of time, and the vertical direction schematically shows the LSI current value. After setting the antenna parameters for tuning, the control unit 140 increases the unit voltage for each control voltage value of the DAC133 in each step, thereby detecting a change in the LSI current and detecting a minimum value (or a maximum value). Then, communication is performed by setting communication antenna parameters.
The detection period of the minimum value (or maximum value) of the LSI current is preferably 50 to 100 [ mu ] s. This is a sufficiently small value compared with 300ms of the discovery time described later.
Here, as shown in fig. 9, as the magnitude of the LSI current, that is, the gain of the oscillation signal from the output unit 135, the gain is set so that the value (second value) during the detection period becomes larger than the value (first value) during communication. Thus, the SN ratio of the current signal can be increased at the time of detection, and therefore the control unit 140 can obtain an accurate optimum control value. For example, the second value is preferably 1.5 to 2 times the first value, but may be set within the allowable current range of the LSI.
< after factory leaving factory >
Fig. 10 is a flowchart showing a process in which the contactless communication apparatus automatically tunes the resonant frequency when the contactless communication apparatus is used by, for example, a user after factory shipment of the contactless communication apparatus. The tuning process of the present embodiment is as follows: when the non-contact communication apparatus (or the electronic device on which the non-contact communication apparatus is mounted) performs the discovery process, the tuning process shown in fig. 8 is performed when a predetermined condition is satisfied. The discovery treatment refers to the following treatment: for example, when the contactless communication device has both the R/W function and the card function, the device having the R/W function and the device having the card function are alternately replaced, and the 2 nd-side device is detected. Specifically, the following processing is performed.
When the initial mode is the R/W mode (step 201), the control unit 140 monitors whether or not an IC card is present in the periphery as the 2-time side device (step 202). In step 202, the contactless communication device outputs an oscillation signal at regular time intervals, thereby detecting the presence or absence thereof.
The control unit 140 starts communication if an IC card is present, and switches the operation mode from the R/W mode to the card mode if no IC card is present (step 203). Further, the control unit 140 monitors whether or not there is R/W as the partner device (step 204).
The control unit 140 starts communication when there is R/W, and detects whether or not time-out occurs if there is no R/W (step 205). For example, in step 203, the control unit 140 may start the timer accumulation at the timing of switching to the card mode, and repeat the processing of steps 202 to 204 until the time elapses.
If a timeout occurs in step 205, the discovery is stopped and the system shifts to a low power consumption mode such as standby in order to reduce power consumption of the contactless communication device, for example. Further, the control unit 140 executes the tuning processing of steps 101 to 107 shown in fig. 8 (step 206). Thereby, the discovery process is ended.
In step 205, the case where the timeout occurs is mainly assumed to be a case where the peripheral IC card and the R/W do not exist, and the user uses the contactless communication device as a device having another function (or does not use it at all). Therefore, in this case, since the contactless communication device is considered to be in a stable state without interference, it is an optimum time for performing tuning processing after factory shipment. Therefore, in the case of a timeout, the discovery process is generally terminated as it is, but in this embodiment, the tuning process shown in fig. 8 is executed in this case.
In this example, the processing from ST101 to ST107 in fig. 8, that is, the case where the LSI current is detected to be the minimum or the maximum in step 206 where the tuning processing is performed will be described. However, instead of such tuning processing, the tuning processing may be executed by detecting other values to detect the optimum control value and detecting the optimum control value. The other values include the following examples (1) to (4).
(1) A control voltage value at which the phase of the antenna current, which is a current flowing through the antenna coil, becomes 0;
(2) the antenna current becomes the minimum or maximum control voltage value;
(3) a control voltage value at which the phase of the antenna impedance becomes 0;
(4) the phase of the LSI current becomes a control voltage value of 0.
The point where the phases (1), (3), and (4) become 0 corresponds to the point of phase 0 ° of the curve shown by the broken line in fig. 4.
Fig. 4 shows simulation results, and it should be noted that the point at-270 ° with respect to the antenna current phase of (1) corresponds to the original phase 0 °, and the point at-180 ° with respect to the LSI current phase of (4) corresponds to the original phase 0 °.
As described above, the tuning period is 50 to 100 μ s, so that the power consumption can be substantially ignored and the user is not aware of the tuning process.
Fig. 11 shows a timing chart of the process shown in fig. 10. The method of observing this timing chart is the same as the case shown in fig. 9. The waiting period of the IC card in steps 201 and 202, the antenna parameter setting period for tuning, the detection period of the minimum value or the maximum value of the LSI current, and the antenna parameter setting period for communication, which are the processing shown in fig. 8, are provided. During the waiting period of the IC card and after the end of the discovery, the LSI current value in the vertical direction becomes the minimum value (actually, there is a case where no current flows), which indicates a state where no oscillation signal is generated.
In this example, the case where the contactless communication device has both the R/W function and the card function has been described, but the same processing can be performed also in a contactless communication device having only the R/W function or only the card function. For example, when the contactless communication device has only the R/W function, it is possible to monitor whether or not an IC card is present in the periphery as the R/W function, and when the presence of the IC card is not detected, it is only necessary to perform a timeout. When the contactless communication device has only the card function, it is possible to monitor whether or not there is R/W in the periphery as the card function, and when the presence of R/W is not detected, it is sufficient to set a timeout.
(conclusion)
As described above, in the contactless communication device of the present embodiment, the measurement unit measures the output current from the oscillation unit 131, the control unit 140 detects the minimum value or the maximum value of the output current, and the resonance frequency is controlled using the optimum control value corresponding to the minimum value or the maximum value. Therefore, even when the resonance frequency fluctuates due to variations in manufacturing, use environments, or time changes of the antenna characteristics, good communication characteristics based on the set resonance frequency can be obtained.
In the contactless communication device of the present embodiment, the differential amplifier a3, which is a measurement unit of the LSI current, is provided in the antenna driving unit 130. Therefore, it is not necessary to provide a resistor and wiring for monitoring the antenna current in the antenna resonance unit 110 between the antenna resonance unit 110 and the antenna driving unit 130, as in patent document 1. In addition, the number of terminals of the antenna driving unit 130 is not increased, and thus a simple circuit configuration can be formed. This makes it possible to simplify the design of the antenna driving unit 130 and to reduce the cost. In addition, noise is less likely to be generated, and favorable communication characteristics can be obtained.
Since the contactless communication device according to the present embodiment is configured to be automatically tuned at factory shipment, manual tuning by an operator on a production line is not required. This can reduce the cost.
Due to the usage environment of the contactless communication device and the time variation of the antenna resonance unit 110, the optimal control value at the factory shipment may be different from the optimal control value at the user's use of the contactless communication device. The contactless communication device according to the present embodiment is configured to be capable of performing auto-tuning even when a user uses the contactless communication device after factory shipment, and therefore, can maintain good communication characteristics.
[ second embodiment ]
Next, a second embodiment of the present invention will be explained. In the following description, substantially the same components, functions, and the like included in the device of the first embodiment are denoted by the same reference numerals, and description thereof will be simplified or omitted, and differences will be mainly described.
Fig. 12 shows a circuit configuration of a contactless communication device of the second embodiment. The capacitor unit of the contactless communication device 300 includes a series resonant capacitor unit and a parallel resonant capacitor unit, as in the above-described embodiment. As a difference from the above-described embodiments, the series resonant capacitor section includes, for example, two variable capacitors VC1, VC2, and the parallel resonant capacitor section includes, for example, two fixed capacity capacitors C9, C10. The variable capacitor VC1 is connected in series to capacitors C2 and C5 for DC cut (DC cut), and similarly, the variable capacitor VC2 is connected in series to capacitors C3 and C6. The control unit 140 outputs a control voltage signal Vcnt to the variable capacitors VC1 and VC2 via the DAC133 provided in the antenna drive unit 130, and variably controls these capacities.
By variably controlling the capacity of the series resonant capacitor unit in this way, it is possible to absorb variations in the resonant frequency due to various factors, and obtain good communication characteristics, as in the first embodiment.
[ third embodiment ]
Fig. 13 shows a circuit configuration of a contactless communication device according to a third embodiment of the present invention. In the contactless communication apparatus 400, both the series resonant capacitor section and the parallel resonant capacitor section, which are capacitor sections, include variable capacitance capacitors. The parallel resonant capacitor section is composed of a variable capacitor VC1 similar to the case shown in fig. 2. The series resonant capacitor unit is composed of two variable capacitors VC2, VC3, as in the case shown in fig. 12.
The control unit 140 outputs a control voltage signal Vcnt1 to the variable capacitor VC1 via the DAC (1)135A, and outputs a control voltage signal Vcnt2 to the variable capacitors VC2 and VC3 via the DAC (2)135B, thereby variably controlling these capacities. In the present embodiment, when the capacitance of the parallel resonant capacitor section (variable capacitor VC1) is changed, the tracking adjustment is performed because a change in the capacitance of the series resonant capacitor section (variable capacitors VC2, VC3) is necessary in accordance with the change.
Specifically, for example, the optimum capacitance of the series resonant capacitor portion (or the control value of the DAC (2)133B corresponding thereto) and the change in capacitance of the parallel resonant capacitor portion (or the control value of the DAC (1)133A corresponding thereto) may be associated with each other and stored in the storage unit 141 as a table in advance. Further, in the tuning process, the control unit 140 obtains the optimum control value in step 105 of the flowchart shown in fig. 8, and obtains the optimum control value for the series resonant capacitor unit corresponding to the optimum control value based on the table, thereby controlling the resonant frequency to be optimum.
[ fourth embodiment ]
Fig. 14 is a block diagram showing the configuration of the contactless power supply system 2 in a mode in which the technique of the contactless communication system 1 (see fig. 1) described above is applied to the contactless power supply system 2. Since data communication is also performed in the contactless power supply system 2, this is the same as in the contactless communication system 1. The contactless power supply system 2 is different from the contactless communication system 1 shown in fig. 1 in that a power supply mode is provided, and a charging control unit 219 is provided in the power receiving device 250. A manner corresponding to transceiving two-way communication is shown herein.
The antenna resonance part 110 of the power feeding device 150 is formed of an LC resonance circuit, and has an output frequency of 100 to 200kHz in the electromagnetic induction method known as the Qi format, for example. In this way, when a plurality of systems are allowed as a format, the oscillation frequency used or the specification of the antenna coil in the antenna resonance unit 110 differs depending on the LSI (antenna driving unit 130).
As the power feeding method of the non-contact power feeding system 2, a method such as electromagnetic induction or magnetic resonance can be applied, but not limited thereto. The power feeding device 150 transmits a carrier signal, and passes a current through the 1 st-order antenna unit 111 to flow through the antenna. A magnetic field generated by a current flowing through the antenna coil magnetically couples with the secondary-2 antenna unit 201 of the power receiving device 250, whereby a voltage is excited in the secondary-2 antenna unit 201 to transmit energy.
In the communication state of the contactless communication system 1, the communication distance between the transmission device 100 and the reception device 200 is long and the distance changes. However, for example, in the electromagnetic induction system known as the Qi format as the power feeding system, since the power receiving device 250 (for example, a mobile phone device) is provided in the power feeding device 150 (for example, a power feeding transmission station), the distance between the two is always substantially constant. The problem that the power feeding device 150 and the power receiving device 250 of the contactless power feeding system 2 each have a resonance circuit and the resonance frequency thereof is shifted due to positional deviation or a device to which power is fed is the same as the problem of the contactless communication system 1 (solved in the contactless communication system 1).
Specifically, the 1 st-order antenna unit 111 and the 2 nd-order antenna unit 201 are configured by a resonant circuit so as to resonate at a carrier frequency for efficient transmission. In general, since energy efficiency is determined by multiplication of a coupling coefficient k of electromagnetic inductive coupling and a Q value of the antenna, a larger k and a higher Q are preferable. However, when the Q of the resonant circuit is increased, the resonant frequency is greatly deviated due to the deviation of the constant, and therefore, it is necessary to use a highly accurate member or adjust the resonant frequency as described above.
Fig. 15 shows a sequence from detection of a power receiving device (equipment detection) in power feeding device 150 to charging (power transmission). The contactless power supply system 2 transmits energy and modulates the magnitude of a carrier signal, thereby performing data communication, and performs device authentication or a request for a required amount of power to be received. For example, in the Qi format, the power receiving device 250 transmits various data by modulating a carrier wave by changing load modulation, that is, the size of a load.
In the case of non-contact power feeding, the power feeding device 150 intermittently supplies a current to the 1 st-order side antenna unit 111 for a short time of generally 50 to 100 μ s, and determines that the power receiving device 250 is installed when the current value changes. This corresponds to reaction confirmation (PING). Although shown as "signal strength" in fig. 15, power feeding device 150 actually detects a change in current of primary antenna unit 111. Therefore, in a state where there is no change in the current, power supply device 150 starts the tuning process shown in fig. 8, and thus tuning can be performed in the same manner as in the above-described embodiment even after factory shipment of the product. When the authentication is OK, the power supply device 150 operates in the power transfer mode to transfer power to the power receiving device 250. In this case, power supply device 150 intermittently performs identification processing for long-time charging, thereby ensuring safety.
[ other embodiments ]
The present invention is not limited to the above-described embodiments, and various other embodiments can be realized.
In the above-described embodiment, at the time of communication, the control section 140 controls the resonance frequency using the optimum control value as the control voltage value for the variable capacitor VC 1. However, the resonance frequency is not necessarily limited to the optimum control value, and may be controlled by a control value corresponding to, for example, an adjacent value of the minimum or maximum value of the LSI current. That is, the control unit 140 may control the resonance frequency with a control value in an arbitrary range including the optimum control value.
In the first and second embodiments, the parallel resonant capacitor unit is configured by 1 variable capacitor VC1, but may be configured by a plurality of variable capacitors.
In each of the above embodiments, the control unit 140 and the storage unit 141 are provided outside the antenna drive unit 130 as shown in fig. 2 and the like, for example, but they may be provided inside the antenna drive unit 130 or may be provided integrally with an LSI, for example.
At least two of the features of the above-described aspects may also be combined.
Description of the symbols
VC1, VC2 and VC3 … variable capacitor
L3 … antenna coil
1 … non-contact communication system
2 … non-contact power supply system
100. 300, 400 … transmitter (non-contact communication device)
110 … antenna resonating section
113 … transmission/reception control unit
119 … control signal line
129 … input line
130 … antenna driving part
131 … oscillating part
132 … gain controller
133…DAC
134…ADC
135 … output part
139 … control value input part
140 … control part
141 … storage unit
150 … power supply device
250 … powered device

Claims (19)

1. A non-contact communication device is characterized by comprising:
an antenna resonance section including an antenna coil and a capacitor section having a variable-capacity capacitor;
an oscillation unit capable of outputting a signal to the antenna resonance unit;
an output unit configured to supply the oscillation signal obtained by the oscillation unit to the antenna resonance unit;
a measuring unit that measures an output current from the output unit; and
and a control unit that detects a minimum value or a maximum value of the measured output current and controls the resonance frequency of the antenna resonance unit using a control value in an arbitrary range including an optimum control value at which the output current is at a minimum or a maximum in a control signal for controlling the capacitance of the variable capacitor of the capacitor unit.
2. The contactless communication device of claim 1,
the oscillation unit outputs a signal having an oscillation frequency shifted from a predetermined frequency, which is a frequency of a signal in which an antenna current, which is a current flowing through the antenna coil, has a minimum value or a maximum value.
3. The contactless communication device of claim 1,
the control unit performs control using a value that is offset from a control value at which the output current is at a minimum or a maximum, among the control values in the arbitrary range.
4. The contactless communication device of claim 1,
the oscillation unit and the measurement unit are provided in an antenna drive unit connected to the antenna resonance unit.
5. The contactless communication device according to claim 1 or 2,
the contactless communication device further includes a storage unit that stores the optimal control value.
6. The contactless communication device according to any one of claims 1 to 3,
the non-contact communication device further includes a gain controller for adjusting a gain of a signal output from the oscillation unit,
the control unit is configured to set the gain, which is one of the antenna parameters, to a first value during a communication period, and to set the gain to a second value different from the first value during a detection period of a minimum value or a maximum value of the output current.
7. The contactless communication device of claim 6,
the second value is greater than the first value.
8. The contactless communication device of claim 1,
the capacitor part includes at least 1 of a series resonance capacitor part and a parallel resonance capacitor part.
9. The contactless communication device of claim 8,
the capacitor section includes both the series resonant capacitor section and the parallel resonant capacitor section.
10. The contactless communication device of claim 9,
the parallel resonant capacitor section has the variable capacitance capacitor,
the series resonant capacitor section has a fixed-capacity capacitor.
11. The contactless communication device of claim 9,
the parallel resonant capacitor section has a fixed capacity capacitor,
the series resonant capacitor section has the variable capacitance capacitor.
12. The contactless communication device of claim 9,
the parallel resonance capacitor section and the series resonance capacitor section each have the variable capacitance capacitor.
13. An antenna circuit of a non-contact communication device including an oscillation unit, a measurement unit, and a control unit, the antenna circuit comprising:
an antenna coil;
a capacitor unit having a variable capacitance capacitor;
an input line to which a signal having an oscillation frequency set by the oscillation unit is input; and
a control signal line connected to the variable capacitance capacitor,
the measuring section measures an output current from an output section that supplies the oscillation signal obtained by the oscillation section to the antenna resonance section,
the control signal line is supplied with a control value in an arbitrary range including an optimum control value, which is the optimum control value among the control signals outputted from the control unit and controlling the capacitance of the variable capacitance capacitor, and which corresponds to the minimum value or the maximum value of the output current from the oscillation unit to the antenna circuit measured by the measurement unit.
14. An antenna driving device that drives an antenna resonance unit including an antenna coil and a capacitor unit having a variable-capacitance capacitor, the antenna driving device comprising:
an oscillation unit capable of outputting a signal to the antenna resonance unit;
an output unit configured to supply the oscillation signal obtained by the oscillation unit to the antenna resonance unit;
a measuring unit that measures an output current from the output unit to the antenna resonance unit; and
and a control value input unit configured to input a control value to the control value input unit, the control value being a control value in an arbitrary range including an optimum control value at which the measured output current is at a minimum or a maximum, among control signals for controlling the capacitance of the variable capacitor, in order to control the resonance frequency of the antenna resonance unit.
15. A non-contact power feeding device is characterized by comprising:
an antenna resonance section including an antenna coil and a capacitor section having a variable-capacity capacitor;
an oscillation unit capable of outputting a signal to the antenna resonance unit;
an output unit configured to supply the oscillation signal obtained by the oscillation unit to the antenna resonance unit;
a measuring unit that measures an output current from the output unit to the antenna resonance unit; and
and a control unit that detects a minimum value or a maximum value of the measured output current and controls the resonance frequency of the antenna resonance unit using a control value in an arbitrary range including an optimum control value at which the output current is at a minimum or a maximum in a control signal for controlling the capacitance of the variable capacitor of the capacitor unit.
16. A tuning method of a resonance frequency of an antenna resonance section including an antenna coil and a capacitor section having a variable-capacity capacitor, characterized in that, in the tuning method,
an oscillation frequency of a signal outputted to the antenna resonance section is set in the oscillation section,
measuring an output current from an output unit for supplying the oscillation signal obtained by the oscillation unit to the antenna resonance unit,
detecting a minimum or maximum value of the measured output current,
a control value is stored in a storage unit, the control value being a control value in an arbitrary range including an optimum control value at which the output current becomes minimum or maximum, among control signals for controlling the capacitance of the variable capacitance capacitor of the capacitor unit.
17. A discovery method performed by a contactless communication device having an antenna resonance portion including an antenna coil and a capacitor portion having a variable-capacity capacitor, characterized in that, in the discovery method,
the presence of the partner side device is detected in R/W (read/write) mode,
detecting the presence of the counterpart side device in the card mode in a case where the presence of the counterpart side device is not detected,
performing a tuning process of a resonance frequency of the antenna resonating section by detecting an optimum control value in a control signal that controls a capacity of the variable-capacity capacitor when the presence of the counterpart device is not detected in the card mode,
the execution of the tuning process includes the acts of: storing the control value in an arbitrary range including the optimum control value in a storage unit,
the optimum control value is a control value at which a phase of an antenna current, which is a current flowing through the antenna coil, becomes 0, a control value at which the antenna current becomes minimum or maximum, a control value at which a phase of an impedance becomes 0, a control value at which a phase of an output current from the oscillation unit to the antenna resonance unit becomes 0, or a control value at which the output current becomes minimum or maximum.
18. The discovery method of claim 17,
the execution of the tuning process includes the acts of:
an oscillation frequency of a signal outputted to the antenna resonance section is set in the oscillation section,
measuring an output current from the oscillator to the antenna resonator,
detecting a minimum or maximum value of the measured output current,
and a control value in an arbitrary range including the optimum control value at which the output current is the minimum or the maximum, among the control signals, is stored in the storage unit.
19. The discovery method of claim 17,
and when the presence of the partner device is not detected in the card mode, repeating the detection in the R/W mode and the detection in the card mode in this order, and when a processing time of repeating the detection in the R/W mode and the detection in the card mode is timed out, executing the tuning.
CN201580038891.2A 2014-07-18 2015-07-09 Communication device, circuit, driving device, power supply device, tuning and discovery method Active CN106537801B (en)

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JP2014148054A JP5839629B1 (en) 2014-07-18 2014-07-18 Non-contact communication device, antenna circuit, antenna drive device, non-contact power supply device, tuning method, discovery method, and program for realizing these methods
PCT/JP2015/069759 WO2016009937A1 (en) 2014-07-18 2015-07-09 Noncontact communication apparatus, antenna circuit, antenna drive apparatus, noncontact feeding apparatus, electronic device, tuning method, discovery method, and programs for achieving these methods

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WO2016009937A1 (en) 2016-01-21
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